Supermassive black holes, long revered as the universe's ultimate apex predators, are apparently quite terrible at dispatching stars efficiently, according to new research from Syracuse University astrophysicists. These enormous objects, weighing millions or even billions of times more than the sun, are known for creating the strongest gravitational environments. Yet, when a star passes dangerously close, total destruction is not always immediate. Instead, some stars merely endure repeated, partial dismemberment, generating a fresh burst of light—and a fresh round of astrophysical head-scratching—with each agonizing return.
For years, the scientific community was perplexed not by the stars’ ongoing trauma, but by why the observational flares from these "repeating partial tidal disruption events" became steadily fainter. Theoretical models consistently failed to reproduce this baffling trend. "We were puzzled by this for two years," admitted doctoral student Ananya Bandopadhyay, whose team has now unveiled the crucial, previously underappreciated factor: how rapidly the star was spinning before its first encounter with the black hole.
Their new simulations reveal that a rapidly spinning star cannot be spun up nearly as much during subsequent passages. Without this dramatic increase in rotation, the stripped stellar material falls back to the black hole at a relatively steady pace. This means as less material is torn away from the star with each pass, the peak brightness of the flare also decreases, finally matching the observed fading light show. The celestial equivalent of a fading reality TV series, it seems, has a scientific explanation.
The amount of material stripped depends heavily on a star's internal structure. A low-mass star, likened by Bandopadhyay to a "fluffy meringue," can become increasingly susceptible to the black hole’s grip, allowing for prolonged, incremental erosion. A higher-mass star, with an "onion-like internal structure," might lose its outer layers while its dense core remains comparatively unchanged, making its later acts of dismemberment less dramatic. In either case, the black hole seems content to take its sweet time.
This begs another question: why would a star approaching a supermassive black hole already be spinning so quickly and locked into such a tight, torturous orbit? Associate professor Eric Coughlin suggests a process known as the Hills mechanism provides the answer. In this cruel cosmic divorce, two stars orbiting each other approach a black hole, which then rips their binary system apart. One star is hurled away to freedom, while its former partner is captured and forced into a slow, grinding demise around the black hole. Coughlin noted this was a major theoretical step forward in understanding such systems.
Now, if only they could figure out why nobody thought to ask the black hole to speed things up a bit.
